The present disclosure generally relates to a locomotive diesel engine and, more specifically, to a burner arrangement for optimizing an exhaust aftertreatment system. The present disclosure exhaust aftertreatment systems may be implemented with a locomotive two-stroke uniflow scavenged diesel engine. This burner arrangement controls the temperature of exhaust at the exhaust aftertreatment system to control oxidation of soot on the filter thereof. As a result, the burner arrangement reduces NOX emissions.
FIG. 1a illustrates a locomotive 103 including a conventional uniflow two-stroke diesel engine system 101. As shown in FIGS. 1b and 1c, the locomotive diesel engine system 101 of FIG. 1a includes a conventional air system. Referring concurrently to both FIGS. 1b and 1c, the locomotive diesel engine system 101 generally comprises a turbocharger 100 having a compressor 102 and a turbine 104, which provides compressed air to an engine 106 having an airbox 108, power assemblies 110, an exhaust manifold 112, and a crankcase 114. In a typical locomotive diesel engine system 101, the turbocharger 100 increases the power density of the engine 106 by compressing and increasing the amount of air transferred to the engine 106.
More specifically, the turbocharger 100 draws air from the atmosphere 116, which is filtered using a conventional air filter 118. The filtered air is compressed by a compressor 102. The compressor 102 is powered by a turbine 104, as will be discussed in further detail below. A larger portion of the compressed air (or charge air) is transferred to an aftercooler (or otherwise referred to as a heat exchanger, charge air cooler, or intercooler) 120 where the charge air is cooled to a select temperature. Another smaller portion of the compressed air is transferred to a crankcase ventilation oil separator 122, which evacuates the crankcase 114 in the engine; entrains crankcase gas; and filters entrained crankcase oil before releasing the mixture of crankcase gas and compressed air into the atmosphere 116.
The cooled charge air from the aftercooler 120 enters the engine 106 via an airbox 108. The decrease in charge air intake temperature provides a denser intake charge to the engine, which reduces NOX emissions while improving fuel economy. The airbox 108 is a single enclosure, which distributes the cooled air to a plurality of cylinders. The combustion cycle of a diesel engine includes, what is referred to as, scavenging and mixing processes. During the scavenging and mixing processes, a positive pressure gradient is maintained from the intake port of the airbox 108 to the exhaust manifold 112 such that the cooled charge air from the airbox 108 charges the cylinders and scavenges most of the combusted gas from the previous combustion cycle.
More specifically, during the scavenging process in the power assembly 110, the cooled charge air enters one end of a cylinder controlled by an associated piston and intake ports. The cooled charge air mixes with a small amount of combusted gas remaining from the previous cycle. At the same time, the larger amount of combusted gas exits the other end of the cylinder via four exhaust valves and enters the exhaust manifold 112 as exhaust gas. The control of these scavenging and mixing processes is instrumental in emissions reduction as well as in achieving desired levels of fuel economy.
Exhaust gases from the combustion cycle exit the engine 106 via an exhaust manifold 112. The exhaust gas flow from the engine 106 is used to power the turbine 104 of the turbocharger 100, and thereby power the compressor 102 of the turbocharger 100. After powering the turbine 104, the exhaust gases are released into the atmosphere 116 via an exhaust stack 124 or silencer.
The exhaust gases released into the atmosphere by a locomotive diesel engine include particulates, nitrogen oxides (NOX) and other pollutants. Legislation has been passed to reduce the amount of pollutants that may be released into the atmosphere. Traditional systems have been implemented which reduce these pollutants, but at the expense of fuel efficiency.
The various embodiments of the present disclosure aftertreatment system are able to exceed, what is referred in the industry as, the Environmental Protection Agency's (EPA) Tier II (40 CFR 92), Tier III (40 CFR 1033), and Tier IV (40 CFR 1033) emission requirements, as well as the European Commission (EURO) Tier IIIb emission requirements. These various emission requirements are cited by reference herein and made a part of this patent application.
In accordance with an embodiment of the disclosure, an exhaust aftertreatment system for a locomotive is described for reducing pollutants. This system generally includes a turbocharger mixing manifold adapted to receive exhaust from the locomotive engine and stabilize the exhaust from the locomotive engine; a filtration system coupled to the turbocharger mixing manifold including a catalyst and filter adapted to filter particulate matter, hydrocarbons and carbon monoxide from the exhaust; and a NOX reduction system situated inline with the filtration system adapted to reduce NOX from the exhaust.
According to various aspects of the present disclosure, the exhaust aftertreatment system may include various additional features. In one embodiment, the exhaust aftertreatment system includes a filtration injection system adapted to add fuel to the exhaust in the turbocharger mixing manifold, where the turbocharger mixing manifold is sized and shaped to promote mixing of the exhaust and fuel contained therein. Specifically, the fuel in this mixture reacts with oxygen in the presence of the catalyst, increasing the temperature of the exhaust, and thereby promoting oxidation of soot on the filter in the filtration system. The filtration system may be comprised of a diesel oxidation catalyst (DOC) or a diesel particulate filter (DPF). A filtration control system is also described for monitoring and controlling particulate buildup on the filter.
In another embodiment, the NOX reduction system may include a selective catalytic reduction (SCR) catalyst and an ammonia slip catalyst (ASC). A NOX reduction control system is also described for monitoring and controlling the NOX reduction system. A NOX reduction system injection system may further be provided to add a NOX reduction reagent to the exhaust. The NOX reduction system injection system is preferably situated upstream of the NOX reduction system.
In yet another embodiment, the exhaust aftertreatment system may further include a heating device, such as a burner, situated with respect to the turbocharger mixing manifold for heating the exhaust and a control system for the heating device. Specifically, this burner arrangement controls the temperature of exhaust at the exhaust aftertreatment system to control oxidation of soot on the filter thereof. As a result, the burner arrangement reduces NOX emissions.
Various embodiments of an exhaust aftertreatment system are shown and described which may operate within a locomotive operating environment and be placed within the limited size constraints of the locomotive. In one embodiment, an exhaust aftertreatment system is shown and described having a filtration system situated inline with a NOX reduction system. In another embodiment, an exhaust aftertreatment system is shown having an integral housing having a filtration system and a NOX reduction system. Because exhaust from a locomotive engine is generally not uniform, the turbocharger mixing manifold may be sized and shaped to uniformly distribute the exhaust to the filtration system. For example, the turbocharger mixing manifold may be sized and shaped such that the exhaust enters a volume greater than the volume at which exhaust is expelled from the engine.
According to another aspect of the present disclosure, an exhaust aftertreatment system is provided for a locomotive, which includes a support system and a connection system to the locomotive engine and structure. The exhaust aftertreatment system includes a turbocharger mixing manifold coupled to an exhaust outlet of the locomotive engine and an emissions reduction system flexibily coupled to the turbocharger mixing manifold to isolate operational loads of the engine from the locomotive. In one example, a support structure is provided such that the mass load of the exhaust aftertreatment system is supported by the locomotive via the support structure. In another example, a connection system is provided to permit the exhaust aftertreatment system to move relative to its loads and account for thermal expansion.
These exhaust aftertreatment systems may be used in conjunction with various exhaust gas recirculation systems (including those described herein) to further reduce exhaust emissions from the engine.
It will be noted that many industries utilize a device commonly known as a burner to mix combustible fuel with air for the purpose of heating either additional gas or the outside of a vessel which may contain gas, liquid or even solid material. Most burners employ an internal combustion chamber where the exhaust gas mixes with fuel and typically external air before ignitions occurs via a heat generating source (e.g. spark plug). Some applications, such as road traveling cars and trucks, direct the flow of all exhaust gas from their engines, through such a burner device for the purpose of increasing the exhaust gas temperature. As such, the burner assembly body remains integral with the exhaust gas conveyance pipes.
Typically, all exhaust gas for a diesel engine aftertreatment system is routed through one or more burners, and partial flow designs mount directly to the engine exhaust manifold using simple pressure-based bypass valve. The current practice of mounting a burner directly to the engine exhaust components, while limiting initial costs and packaging requirements, does so at the expense of reliability and serviceability. Furthermore, the locomotive environment remains a difficult combination of excessive heat and vibration that is not common in road traveling automobiles and trucks. Although there are several competing designs currently available, the conventional burner devices do not possess the necessary robustness in their current state of development.
Further, a burner designed to increase the temperature of exhaust gas upstream of a locomotive aftertreatment system remains a complicated apparatus which controls the addition of burning diesel fuel into the exhaust. Additionally, the design of mixing components within the burner creates aerodynamic turbulence which increases pressure losses for the entire engine exhaust system.
Accordingly, it is a general object of the present disclosure to provide an exhaust aftertreatment system which reduces the amount of pollutants (e.g. particulates, nitrogen oxides (NOX) and other pollutants) released by the diesel engine while achieving desired fuel efficiency.
It is a more specific object of the present disclosure to provide a burner arrangement for a two-stroke locomotive diesel engine having an exhaust aftertreatment system.
It is yet another object of the disclosure to provide a burner arrangement that only requires a portion of the main exhaust flow to raise the bulk temperature of the exhaust to minimize the losses due to the aerodynamic turbulence of the mixing components within the burner.
Still another object of the present disclosure is to provide an external mounting of the burner to improve reliability through isolation from excessive thermal load as well as engine vibration.
Yet another object of the present disclosure is to provide a burner configuration that improves maintenance due to the modularity inherent in the mounting arrangement.
Yet still another object of the present disclosure is to provide a burner that is physically isolated and ensures improved serviceability.
The following description is presented to enable one of ordinary skill in the art to make and use the disclosure and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiment and the generic principles and features described herein will be readily apparent to those skilled in the art. Thus, the present disclosure is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features described herein.